Compositions of neutral layer for directed self assembly block copolymers and processes thereof

ABSTRACT

The present invention relates to novel processes for using the neutral layer compositions for aligning microdomains of directed self-assembling block copolymers (BCP). The processes are useful for fabrication of electronic devices. The novel processes comprise a step of forming a coating of the neutral layer from the neutral layer composition, wherein the neutral layer composition comprises at least one random copolymer having at least one unit of structure (1), at least one unit of structure (2) and at least one unit of structure (3) 
                         
where R 1  is selected from the group consisting of a C 1 -C 8  alkyl, C 1 -C 8  fluoroalkyl moiety, C 1 -C 8  partially fluorinated alkyl, C 4 -C 8  cycloalkyl, C 4 -C 8  cyclofluoroalkyl, C 4 -C 8  partially fluorinated cycloalkyl, and a C 2 -C 8  hydroxyalkyl; R 2 , R 3  and R 5  are independently selected from a group consisting of H, C 1 -C 4  alkyl, CF 3  and F; R 4  is selected from the group consisting of H, C 1 -C 8  alkyl, C 1 -C 8  partially fluorinated alkyl and C 1 -C 8  fluoroalkyl, n ranges from 1 to 5, R 6  is selected from the group consisting of H, F, C 1 -C 8  alkyl and a C 1 -C 8  fluoroalkyl and m ranges from 1 to 3.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional application of Ser. No. 13/243,640filed Sep. 23, 2011 the contents of which are hereby incorporated hereinby reference.

FIELD OF THE INVENTION

The invention relates to novel neutral layer compositions and novelmethods for using the neutral layer compositions for aligningmicrodomains of directed self-assembling block copolymers (BCP). Thecompositions and processes are useful for fabrication of electronicdevices.

DESCRIPTION OF THE INVENTION

Directed self assembly of block copolymers is a method useful forgenerating smaller and smaller patterned features for the manufacture ofmicroelectronic devices in which the critical dimensions (CD) offeatures on the order of nanoscale can be achieved. Directed selfassembly methods are desirable for extending the resolution capabilitiesof microlithographic technology. In a conventional lithography approach,ultraviolet (UV) radiation may be used to expose through a mask onto aphotoresist layer coated on a substrate or layered substrate. Positiveor negative photoresists are useful and these can also contain arefractory element such as silicon to enable dry development withconventional integrated circuit (IC) plasma processing. In a positivephotoresist, UV radiation transmitted through a mask causes aphotochemical reaction in the photoresist such that the exposed regionsare removed with a developer solution or by conventional IC plasmaprocessing. Conversely, in negative photoresists, UV radiationtransmitted through a mask causes the regions exposed to radiation tobecome less removable with a developer solution or by conventional ICplasma processing. An integrated circuit feature, such as a gate, via orinterconnect, is then etched into the substrate or layered substrate,and the remaining photoresist is removed. When using conventionallithographic exposure processes, the dimensions of features of theintegrated circuit feature are limited. Further reduction in patterndimensions are difficult to achieve with radiation exposure due tolimitations related to aberrations, focus, proximity effects, minimumachievable exposure wavelengths and maximum achievable numericalapertures. The need for large-scale integration has led to a continuedshrinking of the circuit dimensions and features in the devices. In thepast, the final resolution of the features has been dependent upon thewavelength of light used to expose the photoresist, which has its ownlimitations. Direct assembly techniques, such as graphoepitaxy andchemoepitaxy using block copolymer imaging, are highly desirabletechniques used to enhance resolution while reducing CD variation. Thesetechniques can be employed to either enhance conventional UVlithographic techniques or to enable even higher resolution and CDcontrol in approaches employing EUV, e-beam, deep UV or immersionlithography. The directed self-assembly block copolymer comprises ablock of etch resistant copolymeric unit and a block of highly etchablecopolymeric unit, which when coated, aligned and etched on a substrategive regions of very high density patterns.

In the graphoepitaxy directed self assembly method, the block copolymersself organizes around a substrate that is pre-patterned withconventional lithography (Ultraviolet, Deep UV, e-beam, Extreme UV (EUV)exposure source) to form repeating topographical features such as aline/space (US) or contact hole (CH) pattern. In an example of a L/Sdirected self assembly array, the block copolymer can form self-alignedlamellar regions which can form parallel line-space patterns ofdifferent pitches in the trenches between pre-patterned lines, thusenhancing pattern resolution by subdividing the space in the trenchbetween the topographical lines into finer patterns. For example, adiblock copolymer which is capable of microphase separation andcomprises a block rich in carbon (such as styrene or containing someother element like Si, Ge, Ti) which is resistant to plasma etch, and ablock which is highly plasma etchable or removable, can provide a highresolution pattern definition. Examples of highly etchable blocks cancomprise monomers which are rich in oxygen and which do not containrefractory elements, and are capable of forming blocks which are highlyetchable, such as methylmethacrylate. The plasma etch gases used in theetching process of defining the self assembly pattern typically arethose used in processes employed to make intergrated circuits (IC). Inthis manner very fine patterns can be created in typical IC substratesthan were definable by conventional lithographic techniques, thusachieving pattern multiplication. Similarly, features such as contactholes can be made denser by using graphoepitaxy in which a suitableblock copolymer arranges itself by directed self assembly around anarray of contact holes or posts defined by conventional lithography,thus forming a denser array of regions of etchable and etch resistantdomains which when etched give rise to a denser array of contact holes.Consequently, graphoepitaxy has the potential to offer both patternrectification and pattern multiplication.

In chemical epitaxy or pinning chemical epitaxy the self assembly of theblock copolymer is formed around a surface that has regions of differingchemical affinity but no or very slight topography to guide the selfassembly process. For example, the surface of a substrate could bepatterned with conventional lithography (UV, Deep UV, e-beam EUV) tocreate surfaces of different chemical affinity in a line and space (L/S)pattern in which exposed areas whose surface chemistry had been modifiedby irradiation alternate with areas which are unexposed and show nochemical change. These areas present no topographical difference, but dopresent a surface chemical difference or pinning to direct self assemblyof block copolymer segments. Specifically, the directed self assembly ofa block copolymer whose block segments contain etch resistant (such asstyrene repeat unit) and rapidly etching repeat units (such as methylmethacrylate repeat units) would allow precise placement of etchresistant block segments and highly etchable block segments over thepattern. This technique allows for the precise placement of these blockcopolymers and the subsequent pattern transfer of the pattern into asubstrate after plasma or wet etch processing. Chemical epitaxy has theadvantage that it can be fined tuned by changes in the chemicaldifferences to help improve line-edge roughness and CD control, thusallowing for pattern rectification. Other types of patterns such asrepeating contact holes (CH) arrays could also be pattern rectifiedusing chemoepitaxy.

Neutral layers are layers on a substrate or the surface of a treatedsubstrate which have no affinity for either of the block segment of ablock copolymer employed in directed self assembly. In the graphoepitaxymethod of directed self assembly of block copolymer, neutral layers areuseful as they allow the proper placement or orientation of blockpolymer segments for directed self assembly which leads to properplacement of etch resistant block polymer segments and highly etchableblock polymer segments relative to the substrate. For instance, insurfaces containing line and space features which have been defined byconventional radiation lithography, a neutral layer allows blocksegments to be oriented so that the block segments are orientedperpendicular to the surface of the substrates, an orientation which isideal for both pattern rectification and pattern multiplicationdepending on the length of the block segments in the block copolymer asrelated to the length between the lines defined by conventionallithography. If a substrate interacts too strongly with one of the blocksegments it would cause it to lie flat on that surface to maximize thesurface of contact between the segment and the substrate; such a surfacewould perturb the desirable perpendicular alignment which can be used toeither achieve pattern rectification or pattern multiplication based onfeatures created through conventional lithography. Modification ofselected small areas or pinning of substrate to make them stronglyinteractive with one block of the block copolymer and leaving theremainder of the surface coated with the neutral layer can be useful forforcing the alignment of the domains of the block copolymer in a desireddirection, and this is the basis for the pinned chemoepitaxy orgraphoepitaxy employed for pattern multiplication.

Thus, there is a need for neutral layer compositions which when formedinto a layer remain neutral to the self assembly block copolymer and yetare not damaged by processing steps of directed self assemblytechniques, and can further enhance the lithographic performance of thedirected self assembly materials and processes, especially reducing thenumber of processing steps and providing better pattern resolution withgood lithographic performance. The present invention relates to novelprocesses and novel neutral layer compositions which form layers whichare neutral to the self assembly block copolymer and provide patternswith good lithographic performance.

DETAILED DESCRIPTION OF DRAWINGS

FIGS. 1 a-1 c show a self alignment process.

FIGS. 2 a-2 i show a process for negative tone line multiplication.

FIGS. 3 a-3 g show a process for positive tone multiplication.

FIGS. 4 a-4 d show a contact hole process.

SUMMARY OF INVENTION

The present invention relates to novel neutral layer compositions andnovel methods for using the neutral layer compositions for aligningmicrodomains of directed self-assembling block copolymers (BCP). Theneutral layer composition comprises at least one random copolymer havingat least one unit of structure (1), at least one unit of structure (2)and at least one unit of structure (3)

where R₁ is selected from the group consisting of C₁-C₈ alkyl, C₁-C₈fluoroalkyl, C₁-C₈ partially fluorinated alkyl, C₄-C₈ cycloalkyl moiety,C₄-C₈ cyclofluoroalkyl moiety, C₄-C₈ partially fluorinated cycloalkylmoiety, and C₂-C₈ hydroxyalkyl; R₂, R₃ and R₅ are independently selectedfrom a group consisting of H, C₁-C₄ alkyl, CF₃ and F; R₄ is selectedfrom the group consisting of H, C₁-C₈ alkyl, C₁-C₈ partially fluorinatedalkyl and C₁-C₈ fluoroalkyl, n ranges from 1 to 5, R₆ is selected fromthe group consisting of H, F, C₁-C₈ alkyl and a C₁-C₈ fluoroalkyl and mranges from 1 to 3.

The present invention also relates to novel processes for formingpatterns using directed self aligned lithography.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to novel neutral layer compositions andnovel self directed assembly processes for forming patterns with highresolution and good lithographic properties. The novel composition iscapable of forming a neutral layer for use with self assembly of blockcopolymers. The neutral layer is an orientation control layer whichallows the block copolymer coated above the neutral layer to align inthe desirable direction relative to the substrate for obtaining highresolution lithography. The invention also relates to novel processesfor use in directed self assembly of block copolymers, such asgraphoepitaxy and chemoepitaxy, which use the neutral layercompositions. The invention leads to further improvement in resolutionor CD uniformity of targeted features made by conventional lithographictechniques, such as UV lithography (450 nm to 10 nm), immersionlithography, EUV or e-beam. The invention relates to neutral layercompositions comprising at least one random crosslinkable polymer. Morethan one polymer may be used in the present novel composition. The novelcomposition comprises only random copolymer(s). The polymer has aneutral interaction with respect to the alignment of the block copolymerused for directed self assembly, but is capable of a high degree ofcrosslinking such that the neutral layer remains neutral and is notdeleteriously affected by the processes that occur over the neutrallayer, such as intermixing with the layers coated over the neutrallayer, developing, irradiation, stripping, etc. The novel polymerunexpectedly provides a neutral layer with an optimal level of bothneutrality to the block copolymers and also crosslinking to preventundesirable damage to the neutral layer due to subsequent processing.

The novel neutral layer composition comprises at least one randompolymer having at least one unit of structure (1), at least one unit ofstructure (2) and, at least one unit of structure (3)

where R₁ is selected from a group consisting of C₁-C₈ alkyl, C₁-C₈fluoroalkyl, C₁-C₈ partially fluorinated alkyl, C₄-C₈ cycloalkyl, C₄-C₈cyclofluoroalkyl, C₄-C₈ partially fluorinated cycloalkyl, and C₂-C₈hydroxyalkyl; R₂, R₃ and R₅ are independently selected from a groupconsisting of H, C₁-C₄ alkyl, CF₃ and F; R₄ is selected from the groupconsisting of H, C₁-C₈ alkyl, C₁-C₈ partially fluorinated alkyl andC₁-C₈ fluoroalkyl, n ranges from 1 to 5, R₆ is selected from the groupconsisting of H, F, C₁-C₈ alkyl, C₁-C₈ fluoroalkyl and C₁-C₈ partiallyfluorinated alkyl, and m ranges from 1 to 3. In one embodiment, R₁ isC₁-C₈ alkyl; R₂, R₃ and R₅ are independently selected from the groupconsisting of H and C₁-C₄ alkyl; R₄ is selected from the groupconsisting of H and C₁-C₈ alkyl and n=1; and R₆ is selected from thegroup consisting of H and C₁-C₈ alkyl and m=1. In another embodiment R₂,R₃ and R₅ is hydrogen, R₁ is C₁-C₈ alkyl, and R₄ and R₆ is hydrogen. Theneutral polymer may be represented by structure 4, where X, Y and Z arethe mole % of the repeat units. In one embodiment the sum of X, Y and Zis 100%.

The novel random polymer can be prepared by a variety of ways by whichalkene containing monomers can be polymerized randomly (such asnitroxide mediated polymerization, cationic, anionic condensation chainpolymerization and the like) but generally they are prepared by radicalpolymerization such as the ones initiated by free radical initiatorssuch as AIBN (azobisisobutyronitrile), benzoyl peroxide or otherstandard thermal radical initiators. These materials also do not need toform a comb like architecture by grafting on a substrate through an endgroup but can simply be spun on as a conventional polymer withoutcovalent attachment to the substrate surface. The present polymer issynthesized such that the concentration of the unit of structure 3 isgreater than 10 mole %; unexpectedly, it has been found that having unit(3) greater than 10 mole % does not destroy neutrality toward the blockcopolymer and has the benefit of dramatically increasing the resistanceof the neutral film to undesirable process damage, such as to solventsafter post applied bake, which show no detectable film loss in organicsolvents. It was generally thought previously that randomizingcomonomers that form the block copolymer would give an acceptableneutral layer polymer; therefore any other comoneric units were kept tothe minimum concentration and typically around 2 mole %, The novelneutral layer can be highly crosslinked so that the solution of theblock copolymer coated over it does not cause intermixing and yetunexpectedly remains neutral to the block copolymer. Unexpectedly,neutrality of the novel neutral layer is sustainable to commonlithographic processing steps such as resist coating, resist soft bake,resist exposure, PEB, resist positive-tune and resist negative-tunedevelopments, and resist stripping using organic solvents and TMAHdevelopers. This in turn has the benefit of eliminating any solventtreatment step needed in many current neutral layers, which are normallyneeded to remove partially crosslinked surface material even after highpost applied bake temperatures (such as 200° C.). Generally, it was thebelief that introducing higher than about 2 mole % of the crosslinkingunit (3) would destroy neutrality toward the self assembly blockcopolymer. Unexpectedly the novel polymer of the present invention iscapable of forming a highly process resistant film which can stillmaintain neutrality toward the self assembly block copolymer despitehaving greater than 10 mole % of the unit of structure (3).Additionally, unexpectedly the novel composition provides and maintainsa crosslinked neutral layer with very good film uniformity across thesubstrate.

The neutral layer comprises units 1, 2 and 3, where unit 1 ranges fromabout 5 mole % to about 90 mole %; unit 2 ranges from about 5 mole % toabout 90 mole % and unit 3 ranges from about 10 mole % to about 60 mole%. In another embodiment the neutral layer comprises units 1, 2 and 3,where unit 1 ranges from about 20 mole % to about 80 mole %; unit 2ranges from about 20 mole % to about 80 mole % and unit 3 ranges fromabout 15 mole % to about 45 mole %.

Herein, alkyl refers to saturated hydrocarbon groups which can be linearor branched (e.g. methyl, ethyl, propyl, isopropyl, tert-butyl and thelike), cycloalkyl refers to a hydrocarbon containing one saturated cycle(e.g. cyclohexyl, cyclopropyl, cyclopentyl and the like), fluoroalkylrefers to a linear or branched saturated alkyl group in which all thehydrogens have been replaced by fluorine, cyclofluoroalkyl refers to acycloalkyl group in which all the hydrogens have been replaced byfluorine, partially fluorinated alkyl refers to a linear or branchedsaturated alkyl group in which part of the hydrogens have been replacedby fluorine, partially fluorinated cycloalkyl refers to a cycloalkylgroup in which part of the hydrogens have been replaced by fluorine,hydroalkyl refers to an alkyl or cycloalkyl group which is substitutedwith a least one hydroxyl moiety (e.g. —CH₂—CH₂—OH, CH—CH(OH)—CH₃ andthe like).

The novel polymer may be used as a single polymer or as blends ofpolymers with differing molecular weight, differing concentrations of arepeat unit containing a benzocyclobutene pendant group (e.g.4-vinyl-benzocyclobutene derived repeat unit), differing comonomerratios, etc. The benzocyclobutene containing monomeric unit can also beemployed with varying amounts of other monomeric units, for example,styrene and methylmethacrylate units can be varied quite substantiallywhile maintaining neutrality towards a block copolymer containing thecorresponding repeat units in a large range of blending compositions.This allows one to optimize a neutral layer for instance by adjustingthe composition of a binary blend containing two different neutralpolymers containing different ratios of repeat units so as to maximizethe effectiveness of a particular self directed approach such agraphoepitaxy or chemoepitaxy in imparting pattern rectification and/orpattern multiplication for a given array of repeating features such asL/S or CH patterns. A single polymer may also be used in the novelcomposition. In one embodiment of the present invention the neutrallayer composition comprises a blend of two or more different compositionof the novel polymer. The composition may comprise a blend of 2 or morepolymers of differing mole % concentration of the units of structure 1,2 and 3. As an example, the composition comprises a first and secondpolymer of differing mole ratios of the monomeric units; a first polymerwhere the unit of structure 1 is from about 5 mole % to about 90 mole %,structure of unit 2 is from about 5 mole % to about 90 mole % andstructure 3 is from about 10 mole % to about 60 mole %; a second polymerwhere the unit of structure 1 is from about 5 mole % to about 90 mole %,structure of unit 2 is from about 5 mole % to about 90 mole % andstructure 3 is from about 10 mole % to about 60 mole %.

The solid components of the neutral layer composition are mixed with asolvent or mixtures of solvents that dissolve the solid components.Suitable solvents may include, for example, a glycol ether derivativesuch as ethyl cellosolve, methyl cellosolve, propylene glycol monomethylether (PGME), diethylene glycol monomethyl ether, diethylene glycolmonoethyl ether, dipropylene glycol dimethyl ether, propylene glycoln-propyl ether, or diethylene glycol dimethyl ether; a glycol etherester derivative such as ethyl cellosolve acetate, methyl cellosolveacetate, or propylene glycol monomethyl ether acetate (PGMEA);carboxylates such as ethyl acetate, n-butyl acetate and amyl acetate;carboxylates of di-basic acids such as diethyloxylate anddiethylmalonate; dicarboxylates of glycols such as ethylene glycoldiacetate and propylene glycol diacetate; and hydroxy carboxylates suchas methyl lactate, ethyl lactate (EL), ethyl glycolate, andethyl-3-hydroxy propionate; a ketone ester such as methyl pyruvate orethyl pyruvate; an alkoxycarboxylic acid ester such as methyl3-methoxypropionate, ethyl 3-ethoxypropionate, ethyl2-hydroxy-2-methylpropionate, or methylethoxypropionate; a ketonederivative such as methyl ethyl ketone, acetyl acetone, cyclopentanone,cyclohexanone or 2-heptanone; a ketone ether derivative such asdiacetone alcohol methyl ether; a ketone alcohol derivative such asacetol or diacetone alcohol; a ketal or acetal like 1,3 dioxalane anddiethoxypropane; lactonessuch as butyrolactone; an amide derivative suchas dimethylacetamide or dimethylformamide, anisole, and mixturesthereof. The composition may further comprise additives such assurfactants.

The novel neutral layer composition is coated on a substrate and heatedto remove the solvent and crosslink the film. Typical film thicknessrange from about 3 nm to about 50 nm after heating, or about 3 nm toabout 30 nm, or about 4 nm to about 20 nm, or about 5 nm to about 20 nm,or about 10 nm to about 20 nm. The film can be heated at temperaturesranging from about 180° C. to about 350° C., or from about 200° C. toabout 300° C. Once the crosslinked film has been formed the coating maybe used for further processing to finally form a pattern using any selfdirected assembly techniques. Examples of such techniques aregraphoepitaxy, standard chemoepitaxy, chemoepitaxy with pinning, etc.The crosslinked neutral layers formed by the novel neutral layercomposition remain neutral despite any damage that might occur duringthe lithographic processes where the crosslinked neutral layer is used,such as dissolution from organic solvents (such as solvents used to formcoatings above the neutral layer, solvent developers, etc), dissolutionin aqueous alkaline developers, damage from processes used to image thephotoresist coated over the neutral layer (such as e-beam, euv, deep uv,etc), or dissolution in photoresist strippers. The crosslinked layersare not soluble in solvents such as those that are used to coat thephotoresist, such as PGMEA, PGME, EL, etc.

The block copolymer for use in directed self assembly in conjunctionwith the novel neutral layer composition can be any block copolymerswhich can form domains through self assembly. The microdomains areformed by blocks of the same type which tend to self associate.Typically, block copolymer employed for this purpose are polymers inwhich the repeat units derived from monomers are arranged in blockswhich are different compositionally, structurally or both and arecapable of phase separating and forming domains. The blocks havediffering properties which can be used to remove one block while keepingthe other block intact on the surface, thus providing a pattern on thesurface. Thus, the block may be selectively removed by plasma etching,solvent etching, developer etching using aqueous alkaline solution, etc.In block copolymers based on organic monomers, one block can be madefrom polyolefinic monomers including polydienes, polyethers includingpoly(alkylene oxides) such as polyethylene oxide), polypropylene oxide),poly(butylene oxide) or mixtures thereof; and, the other block can bemade from different monomers including poly((meth)acrylates),polystyrenes, polyesters, polyorganosiloxanes, polyorganogermanes, andor mixtures thereof. These blocks in a polymer chain can each compriseone or more repeat units derived from monomers. Depending on the type ofpattern needed and methods used different types of block copolymers maybe used. For instance, these may consist of diblock copolymers, triblockcopolymers, terpolymers, or multiblock copolymers. The blocks of theseblock copolymers may themselves consist of homopolymers or copolymers.Block copolymers of different types may also be employed for selfassembly, such as dendritic block copolymers, hyperbranched blockcopolymers, graft block copolymers, organic diblock copolymers, organoicmultiblock copolymers, linear block copolymers, star block copolymersamphiphilic inorganic block copolymers, amphiphilic organic blockcopolymers or a mixture consisting of at least block copolymers ofdifferent types.

The blocks of organic block copolymer may comprise repeat units derivedfrom monomers such as C₂₋₃₀ olefins, (meth)acrylate monomers derivedfrom C₁₋₃₀ alcohols, inorganic-containing monomers including those basedon Si, Ge, Ti, Fe, Al. Monomers based on C₂₋₃₀ olefins can make up ablock of high etch resistance alone or do so in combination with oneother olefinic monomer. Specific example of olefinic monomers of thistype are ethylene, propylene, 1-butene, 1,3-butadiene, isoprene,dihydropyran, norbornene, maleic anhydride, styrene, 4-hydroxy styrene,4-acetoxy styrene, 4-methylstyrene, alpha-methylstyrene or mixturesthereof. Examples of highly etchable units can be derived from(meth)acrylate monomers such as (meth)acrylate, methyl(meth)acrylate,ethyl(meth)acrylate, n-propyl(meth)acrylate, isopropyl(meth)acrylate,n-butyl(meth)acrylate, isobutyl(meth)acrylate, n-pentyl(meth)acrylate,isopentyl(meth)acrylate, neopentyl(meth)acrylate, n-hexyl(meth)acrylate,cyclohexyl(meth)acrylate, isobornyl(meth)acrylate,hydroxyethyl(meth)acrylate or mixtures thereof.

An illustrative example of a block copolymer containing one type of highetch resistant repeat unit would be a polystyrene block containing onlyrepeat units derived from styrene and another type of highly etchablepolymethylmethacrylate block containing only repeat units derived frommethylmethacrylate. These together would form the block copolymerpoly(styrene-b-methylmethacrylate), where b refers to block.

Specific non-limiting examples of block copolymers that are useful forgraphoepitaxy, chemoepitaxy or pinned chemoepitaxy as used for directedself assembly on a patterned neutral layer, are poly(styrene-b-vinylpyridine), poly(styrene-b-butadiene), poly(styrene-b-isoprene),poly(styrene-b-methyl methacrylate), poly(styrene-b-alkenyl aromatics),poly(isoprene-b-ethylene oxide), poly(styrene-b-(ethylene-propylene)),poly(ethylene oxide-b-caprolactone), poly(butadiene-b-ethylene oxide),poly(styrene-b-t-butyl(meth)acrylate), poly(methylmethacrylate-b-t-butyl methacrylate), poly(ethylene oxide-b-propyleneoxide), poly(styrene-b-tetrahydrofuran),poly(styrene-b-isoprene-b-ethylene oxide),poly(styrene-b-dimethylsiloxane), poly(methylmethacrylate-b-dimethylsiloxane), or a combination comprising at leastone of the above described block copolymers. All these polymericmaterials share in common the presence of at least one block which isrich in repeat units resistant to etching techniques typically employedin manufacturing IC devices and at least one block which etches rapidlyunder these same conditions. This allows for the directed self assembledpolymer to pattern transfer onto the substrate to affect either patternrectification or pattern multiplication.

Typically, the block copolymers employed for the directed self assemblysuch as in graphoepitaxy, chemoepitaxy or pinned chemoepitaxy have aweight-averaged molecular weight (M_(w)) in the range of about 3,000 toabout 500,000 g/mol and a number averaged molecular weight (M_(n)) ofabout 1,000 to about 60,000 and a polydispersity (M_(w)/M_(n)) of about1.01 to about 6, or 1.01 to about 2 or 1.01 to about 1.5. Molecularweight, both M_(w) and M_(n), can be determined by, for example, gelpermeation chromatography using a universal calibration method,calibrated to polystyrene standards. This ensures that the polymerblocks have enough mobility to undergo self assembly when applied to agiven surface either spontaneously, or by using a purely thermaltreatment, or through a thermal process which is assisted by theabsorption of solvent vapor into the polymer framework to increase flowof segments enabling self assembly to occur.

Solvents suitable for dissolving block copolymers for forming a film canvary with the solubility requirements of the block copolymer. Examplesof solvents for the block copolymer assembly include propylene glycolmonomethyl ether acetate (PGMEA), ethoxyethyl propionate, anisole, ethyllactate, 2-heptanone, cyclohexanone, amyl acetate, n-butyl acetate,n-amyl ketone (MAK), gamma-butyrolactone (GBL), toluene, and the like.In an embodiment, specifically useful casting solvents include propyleneglycol monomethyl ether acetate (PGMEA), gamma-butyrolactone (GBL), or acombination of these solvents.

The block copolymer composition can comprise additional componentsand/or additives selected from the group consisting of:inorganic-containing polymers; additives including small molecules,inorganic-containing molecules, surfactants, photoacid generators,thermal acid generators, quenchers, hardeners, cross-linkers, chainextenders, and the like; and combinations comprising at least one of theforegoing, wherein one or more of the additional components and/oradditives co-assemble with the block copolymer to form the blockcopolymer assembly.

The block copolymer composition is applied to a pattern of the novelneutral layer which has been defined on a surface by conventionallithography, where the neutral surface is a crosslinked coating formedfrom the novel composition. Upon application and solvent removal, theblock copolymer then undergoes self assembly directed by the specificpattern formed by conventional lithographic processing over the neutrallayer through either actual topographical features or a patternedchemical difference of the substrate surface created by conventionallithographic process. Either pattern rectification maintaining the sameresolution is achieved and/or pattern multiplication may also beachieved if multiple phase boundaries are formed between the featuresdefined with conventional lithography, depending on the relative pitchof the pattern versus the microphase separation distance after standardIC processing to pattern transfer.

The application of the block copolymer by spinning techniques (includingspin drying) can suffice to form the self directed block copolymerassembly. Other methods of self directed domain formation can occurduring applying, baking, annealing, or during a combination of one ormore of these operations. In this way, an oriented block copolymerassembly is prepared by the above method, having microphase-separateddomains that comprise cylindrical microdomains oriented perpendicular tothe neutral surface, or that comprise lamellar domains orientedperpendicular to the neutral surface. Generally, themicrophase-separated domains are lamellar domains oriented perpendicularto the neutral surface, which provide parallel line/space patterns inthe block copolymer assembly. The domains, so oriented, are desirablythermally stable under further processing conditions. Thus, aftercoating a layer of a block copolymer assembly including a useful diblockcopolymer such as, for example, poly(styrene-b-methyl methacrylate), andoptionally baking and/or annealing, the domains of the block copolymerwill form on and remain perpendicular to the neutral surface, givinghighly resistant and highly etchable regions on the surface of thesubstrate, which can be further pattern transferred in the substratelayers. The directed self assembled block copolymer pattern istransferred into the underlying substrate using known techniques. In oneexample wet or plasma etching could be used with optional UV exposure.Wet etching could be with acetic acid. Standard plasma etch process,such as a plasma comprising oxygen may be used; additionally argon,carbon monoxide, carbon dioxide, CF₄, CHF₃, may be present in theplasma. FIGS. 1 a-1 c illustrate a process where the neutral layer ismodified to define a patterned chemical affinity, FIG. 1 a. The blockcopolymer is then coated over a chemically modified neutral layer andannealed to form domains perpendicular to the substrate surface, FIG. 1b. One of the domains is then removed to form a pattern on the surfaceof the substrate, FIG. 1 c.

In the present invention the initial photoresist pattern used forforming the directed self assembly pattern can be defined using eithernegative or positive photoresists, or either positive tone or negativetone development processes, and imageable using any conventionallithographic techniques, such as e-beam, ion beam, x-ray, EUV (13.5 nm),broadband, or UV (450 nm-10 nm) exposure, immersion lithography, etc. Inone embodiment the present invention is particularly useful for 193 nmimagewise exposure using either dry lithography or immersionlithography. For 193 nm lithography a commercially available positive193 nm photoresist can be employed such as the non-limiting example ofAZ AX2110P (available from AZ Electronic Materials USA Corp, Somerville,N.J.), photoresist from Shin-Etsu Chemical Corp., JSR Micro from JapanSynthetic Rubber, and other photoresists available from FujiFilm, TOK,etc. These photoresists may be developed after exposure, and postexposure baked using an aqueous alkaline developer comprisingtetramethylammonium hydroxide to give a positive tone pattern ordeveloped using an organic solvent such as n-amyl ketone (MAK), n-butylacetate, anisole, etc. to give a negative tone pattern. Alternatively,also for 193 nm exposure, commercially available negative tonephotoresists may be employed. One particular feature of the presentinvention is that despite the high level of crosslinking of the neutrallayer, unexpectedly neutrality of the neutral layer toward the blockcopolymer is maintained. The high level of crosslinking is required whenprocessing steps occur, such as overcoating with photoresist, baking thephotoresist, exposing the photoresist, developing the photoresistpattern with the developers employed as described above for each type ofphotoresist, stripping conditions, etc.; but the novel neutral filmstill retains neutrality thus allowing for proper orientation of theblock copolymer domains between the topographical lithographic features.The neutrality is required to control the orientation of the blockcopolymer during the alignment process, such that the domains of theblock copolymer will form on and remain perpendicular to the neutralsurface, as shown in FIGS. 1 a-1 c. FIGS. 1 a-1 c show how the blockcopolymer orients itself into domains perpendicular to the substrate andone of the domains is removes to give a pattern on the substrate.

The substrate over which the neutral layer is coated is any required bythe device. In one example the substrate is a wafer coated with a layerof high carbon content organic layer with a coating of silicon ortitanium containing ARC (high etch resistance to oxygen plasma) over it,which allows pattern transfer of the patterned block copolymer intothese coatings. Suitable substrates include, without limitation,silicon, silicon substrate coated with a metal surface, copper coatedsilicon wafer, copper, aluminum, polymeric resins, silicon dioxide,metals, doped silicon dioxide, silicon nitride, silicon carbide,tantalum, polysilicon, ceramics, aluminum/copper mixtures, glass, coatedglass; gallium arsenide and other such Group III/V compounds. Thesesubstrates may be coated with antireflective coating(s). The substratemay comprise any number of layers made from the materials describedabove.

For the present invention a variety of processes involving graphoepitaxyor (pinned) chemoepitaxy may be employed to achieve a directed selfassembly of the aforementioned block copolymer using a neutral layerwhich is resistant to lithographic processes as described above,especially maintaining neutrality after crosslinking, to control theorientation of the block copolymers relative to the substrate; thisdirected self assembly block copolymer coating is then used to form ahigh resolution pattern using plasma or wet etching to remove the highlyetchable domains of the block copolymer. This pattern can then befurther transferred into the substrate. In this manner, a variety ofhigh resolution features may be pattern transferred into the substrateachieving either pattern rectification, pattern multiplication or both.

As an example, in graphoepitaxy applications, any structure such as aphotoresist pattern, using any photoresist, is formed and imaged overthe novel neutral layer coated on a substrate using standardlithographic techniques. Other neutral layers which are resistant tolithographic processes and maintain neutrality after crosslinking may beused. The pitch of topographical features imaged through standardlithography using a photoresist on top of a neutral layer is larger thanthe pitch of the block copolymer assembly. These topographicalphotoresist features are typically hardened by ultraviolet exposure,baking or a combination of both of these to avoid intermixing of theblockcopolymer with the photoresist. The hardening conditions aredetermined by the type of photoresist used. As an example hardening canbe a bake for 2 minutes at 200° C. with or without a UV exposure. Theblock copolymer composition is used to form a coating and then treatedto form self directed domains as described previously. Consequently, thedomains of the block copolymer assembly (either spontaneously, throughsolvent treatment or thermally by annealing) are forced by theconstraints of the topographical pattern overlying the critical neutrallayer to align in such a way to multiply the spatial frequency of thefine topographical photoresist pattern, that is domains of high etchrate and etch resistant regions are formed perpendicular to thesubstrate surface. This multiplication of special frequency is thenumber of repeating sets of features along a given direction of thetopographical pattern. Thus, the resulting pattern in the blockcopolymer assembly (the spatial frequency of the patterned blockcopolymer assembly) can be doubled, tripled, even quadrupled relative tothe spatial frequency of the original fine topographical pattern. Thesegregation of the domains occurs such that a structure comprisingrepeating sets of domains is formed between the patterned photoresisttopography with a spatial frequency for the domains (given by the numberof repeating sets of domains in the given direction) of at least twicethat of the spatial frequency for the topographical pattern.

In one embodiment, the present invention relates to a process for usinga positive tone photoresist pattern for graphophoepitaxy. A neutrallayer which is resistant to lithographic processes and maintainneutrality after crosslinking may be used. The process comprises forminga coating of the novel neutral layer composition on a substrate surface;baking the neutral layer to form a crosslinked and neutral layer;providing a coating of a positive acting photoresist layer over theneutral layer; forming a positive pattern in the photoresist;optionally, hardening the positive photoresist pattern by hardbaking, UVexposure or a combination of the two; applying a block copolymercomprising an etch resistant block and an etch labile block over theresidual positive photoresist pattern and annealing the film stack untildirected self assembly governed by the residual photoresist feature andneutral layer occurs, such that the domains form perpendicular to thesubstrate surface; and, etching the block copolymer so that the etchlabile blocks are removed producing a line multiplication of theoriginal residual pattern. The neutral layer is such that no damageoccurs to the neutral layer during lithographic processing, as describedpreviously.

In another embodiment, the present invention relates to a process forusing a negative tone photoresist pattern for use in graphoepitaxy. Aneutral layer which is resistant to lithographic processes and maintainneutrality after crosslinking may be used. The process comprises forminga coating of the novel neutral layer on a substrate; baking the neutrallayer to form a crosslinked and neutral layer; providing a coating of anegative acting photoresist layer over the neutral layer; forming anegative tone pattern in the photoresist; optionally, hardening thephotoresist pattern by hardbaking, UV exposure or a combination of thetwo; applying a block copolymer comprising an etch resistant block andan etch labile block to the substrate containing the pattern andannealing the film stack until directed self assembly governed by theresidual photoresist feature and the neutral layer occurs, such that thedomains form perpendicular to the substrate surface; and, etching theblock copolymer so that the etch labile block are removed producing aline multiplication of the original residual pattern. The neutral layeris such that no damage occurs to the neutral layer during lithographicprocessing, as described previously.

In chemoepitaxy, the substrate surface provides a pinning surfacefeature in the novel neutral layer which has a particular chemicalaffinity towards a block of the block copolymer, and it is this affinityand the presence of the neutral layer which orients the alignment of theblock copolymer. A neutral layer which is resistant to lithographicprocesses and maintain neutrality after crosslinking may be used. Thepinning feature may be a patterned photoresist feature on the surface ofthe novel neutral layer or a patterned opening in the novel neutrallayer or a patterned neutral layer whose surface has been suitablytreated to provide a patterned pinning surface. The pinning feature withthe chemical difference can be created by any method, such aslithographic imaging of the photoresist and/or etching of the neutrallayer to expose a patterned surface with a chemical difference, or anyother combination of lithographic techniques. The pinning feature mayalso be created by chemical treatment of the patterned surface of theneutral layer, without removing the neutral layer. Typically, a stack isformed on the substrate comprising a neutral layer coated over asubstrate, over which is coated a photoresist layer.

In one embodiment of a negative tone (where the unexposed region isremoved to form a pattern) line multiplication chemoepitaxy, a coatingof the novel neutral layer is formed on a substrate, such as on anantireflective substrate or any other type of substrate; the neutrallayer is heated to form a crosslinked neutral layer; a coating of aphotoresist layer is formed over the crosslinked neutral layer; and, thephotoresist is imaged to form a pattern with an open or developed trenchin the unexposed regions over the neutral layer and substrate stack.Typically a negative tone is obtained by using a negative photoresistwhich opens the unexposed regions or a positive photoresist which afterforming a latent image in the photoresist uses an organic solvent toremove the unexposed regions, thus forming a trench with a narrowopening. A neutral layer which is resistant to lithographic processesand maintain neutrality after crosslinking may be used. Once the patternis formed over the neutral layer, the trench is treated to have achemical affinity. The chemical affinity can be achieved by anytechnique such as by removing the neutral layer, by wet etching or aplasma etch, or can be treated to form a surface with a particularchemical affinity to one of the blocks of the block copolymer. Typicallyan oxygen containing plasma is used to etch the neutral layer, thusforming a patterned neutral layer over the substrate. The photoresist isthen removed. The photoresist may be removed with a wet stripper, suchas an organic solvent stripper used for that particular photoresist orby an aqueous alkaline developer. The openings in the neutral layer havea chemical affinity to only one of the blocks in the block copolymer. Asan example if the substrate surface is a silicon antireflective coatingor an oxide, it will have an affinity towards the acrylate block and notto the styrene block of the block copolymer, thus forming a patternedpinning surface. One particular feature of the present invention is thatdespite the high level of crosslinking of the neutral layer,unexpectedly, neutrality of the neutral layer is maintained. The highlevel of crosslinking is required when overcoating with photoresist ordeveloping the photoresist pattern with the developers employed, orstripping the photoresist, as described above for each type ofphotoresist; thus allowing for proper orientation of the block copolymerdomains between the pinning areas created by the above describedprocess. The block copolymer composition is then applied over thepatterned neutral layer to form a layer and treated (such as heating toanneal) to form a self aligned block copolymer with domains of an etchresistant block and an etch labile block perpendicular to the substratecontaining the pattern of neutral layer and removed or treated neutrallayer; and, further etching the block copolymer so that the etch labileblocks are removed producing a line multiplication of the originallithographic pattern. Removal of one of the blocks may be by plasma orwet etching. Consequently, the resulting pattern in the block copolymerassembly (i.e., the spatial frequency of the patterned block copolymerassembly) can be doubled, tripled, even quadrupled relative to thespatial frequency of the original fine chemical pattern. The domains, sooriented in this manner, should be thermally stable under the processingconditions. For instance when a layer of a block copolymer assemblyincluding a useful diblock copolymer such as, for example,poly(styrene-b-methylmethacrylate), is coated on a chemically patternedneutral layer, the methylmethacrylate block segments will preferentiallyinteract with the areas of the neutral layer which have been etched ortreated; this creates pinning sites which constrain the domains of theblock copolymer between the pinning sites, and the novel neutral layerforces the block segments of the block copolymer to remain perpendicularto the neutral surface and are constrained by the chemical pattern inthe neutral layer. The domains form by lateral segregation of the blockson the neutral layer between the constraining chemical pattern in theneutral layer. The segregation of the domains occurs such that astructure comprising repeating sets of domains is formed over thechemically patterned neutral layer with a spatial frequency for thedomains (given by the number of repeating sets of domains in the givendirection) of at least twice that of the spatial frequency for theoriginal chemical pattern in the neutral layer. Finally, as before thedirected self assembled block copolymer pattern in transferred into theunderlying substrate using standard plasma or wet etch processes.

In one embodiment of a positive tone line multiplication chemoepitaxy, aconventional positive photoresist may be used to create chemicalpinning. This is accomplished by coating a positive photoresist asdescribed previously on the neutral layer of the present inventioncoated over a substrate and imaging the photoresist such that the imageis overexposed, thus reducing the dimensions of the photoresist patternto create very shallow residual photoresist features, such as residuallines on which the block polymer may be applied. This very shallowfeature has very little topography, about the order of 10 nm to 100 nmwidth and 5 nm to 30 nm height. These residual features act as a pinningarea over the neutral layer when the block copolymer is applied to thesurface of the neutral layer with these residual features remaining. Asdescribed above, the block copolymer form directed self aligned domainsusing the residual features as pinning areas and neutral layer forcesthe alignment to give domains perpendicular to the substrate. Finally,as before the directed self assembled block copolymer pattern intransferred into the underlying substrate using standard plasma or wetetch processes.

In detail, FIGS. 2-4 describe novel processes that use the novel neutralunderlayer to obtain high resolution features of the order of nanometersusing directed self assembly of block copolymers.

In the present processes, any type of substrate may be used. As anexample, a substrate which has a coating of high carbon underlayer and asilicon antireflective coating may be used as a substrate. The highcarbon underlayer can have a coating thickness of about 20 nm to about 2microns. Over this is coated a silicon antireflective coating of about10 nm to about 100 nm. The novel neutral layer composition is used toform a coating over the silicon antireflective coating. The neutrallayer is coated and baked to form a crosslinked layer of thickness ofabout 3 nm to about 30 nm, or about 4 nm to about 20 nm, or about 5 nmto about 20 nm, or about 10 nm to about 20 nm. Over the crosslinkedneutral layer is coated a photoresist which is formed and imaged usingconventional techniques, such as spin coating, baking, and forming animage. FIGS. 2 a-2 i illustrate a negative tone line multiplicationprocess. FIG. 3 a-3 g illustrate a positive tone line multiplicationprocess. FIG. 4 a-4 d illustrate process for contact holemultiplication.

FIG. 2 a-FIG. 2 i illustrate a novel process for forming linemultiplication using a negative tone process. A multilayer stack isformed on a substrate in FIG. 2 a, where the stack comprises a substratecomprising a high carbon underlayer and a silicon antireflective coatinglayer, the novel crosslinked neutral layer and a photoresist layer. Anysubstrate may be used. Any neutral layer which is resistant tolithographic processes and maintains neutrality after crosslinking maybe used. The photoresist may be any that is available such as 193 nmphotoresist, immersion 193 nm photoresist, e beam photoresist, EUVphotoresist, 248 nm photoresist, broadband, 365 nm, 436 nm, etc. Thephotoresist layer is imaged to form a pattern using conventionaltechniques. A negative tone photoresist may be used or a positive tonephotoresist that uses an organic solvent to develop away the unexposedregions to form very narrow trenches may be used, as shown in FIG. 2 b.The novel underlayer is treated to form a pinning surface with aspecific chemical affinity to one of the blocks of the block copolymer,using techniques such as plasma etching to remove the layer, plasmaetching to modify the surface of the layer, or chemically treating thelayer by further deposition of a material or any other pinning methods.A plasma comprising oxygen may be used to remove the neutral layer, asshown in FIG. 2 c. The photoresist is then stripped away using solventstripper or plasma etching, as shown in FIG. 2 d. Solvents such as anyorganic solvents known for removing photoresists may be used, such asPGMEA, PGME, ethyl lactate, etc. The photoresist may also be removed bydeveloping the photoresist pattern in aqueous alkaline developer ascommonly used in removing exposed photoresists. The neutral layer on thesubstrate still maintains its neutrality after the photoresist processsteps. Over the patterned neutral layer, FIG. 2 e, the compositioncomprising the block copolymer is coated and treated (such as annealing)to form a self directed alignment pattern of alternating segments of theblock copolymer. A layer which is neutral is required to cause thealignment of the block copolymer to give regions of high etch resistanceand regions of low etch resistance, such that pattern multiplication canbe achieved, as shown in FIG. 1 e; if the neutral layer was notsufficiently neutral then an undesirable orientation parallel to thesurface would be achieved. A subsequent etch then removes the highlyetchable blocks of the block copolymer, leaving a patterned surface withvery high resolution, as shown in FIG. 2 f. Typical etch to remove oneof the blocks would be a wet or plasma etch as described previously. Thepattern may then be transferred in the lower stack layers by plasmaetching, as shown in FIG. 2 g-2 i, using etchants for the antireflectivecoating stack. Typical etch would be a plasma etch dependent on thesubstrate.

FIGS. 3 a to 3 g illustrates a novel process for forming linemultiplication using a positive tone process. A multilayer stack isformed on a substrate the novel neutral layer and a photoresist layer inFIG. 3 a, where the substrate comprises a high carbon underlayer and asilicon antireflective coating layer. Any neutral layer which isresistant to lithographic processes and maintains neutrality aftercrosslinking may be used. The photoresist may any that are availablesuch as 193 nm photoresist, immersion 193 nm photoresist, e beamphotoresist, EUV photoresist, 248 nm photoresist, etc. The photoresistlayer is imaged to form a pattern using conventional techniques. Apositive tone photoresist is used to form fine photoresist lines, asshown in FIG. 3 b. In some cases the photoresist is overexposed, that isgiven a high energy dose, to form very fine pattern. The very finephotoresist pattern over the novel neutral underlayer is used to form aself aligned pattern using the block copolymer. The compositioncomprising the block copolymer is coated and treated (such as annealing)to form a self directed alignment pattern of alternating segments of theblock copolymer. A layer which is neutral is required to cause thealignment of the block copolymer to give regions of high etch resistanceand regions of low etch resistance, such that pattern multiplication canbe achieved, as shown in FIG. 3 c; if the neutral layer was notsufficiently neutral then an undesirable orientation perpendicular toone shown would be achieved. A subsequent etch then removes the highlyetchable blocks of the block copolymer, leaving a patterned surface withvery high resolution, as shown in FIG. 3 d. Typical etch would be a wetor plasma etch as described previously. The pattern may then betransferred in the lower stack layers by plasma etching, as shown inFIG. 3 e-g. Typical etch would be plasma etch dependent on thesubstrate.

FIG. 4 a-4 d illustrates a novel process for forming contact holemultiplication using a chemoepitaxy process. A multilayer stack isformed on a substrate, where the stack comprises a substrate (such as asilicon antireflective coating layer, a titanium antireflective coating,silicon oxide, etc.), the novel neutral layer and a photoresist layer. Aneutral layer which is resistant to lithographic processes and maintainneutrality after crosslinking may be used. The photoresist may be anythat are available such as 193 nm photoresist, immersion 193 nmphotoresist, e beam photoresist, EUV photoresist, 248 nm photoresist,etc. The photoresist layer is imaged to form a pattern usingconventional techniques, FIG. 4 a. The novel underlayer is treated toform a pinning surface using techniques such as plasma etching to removethe layer, plasma etching to modify the surface of the layer, orchemically treating the layer by further deposition of a material or anyother pinning methods. A plasma comprising oxygen may be used to removethe neutral layer, as shown in FIG. 4 b. The photoresist is thenstripped away using solvent stripper or plasma etching. Solvents such asany organic solvents known for removing photoresists may be used, suchas PGMEA, PGME, ethyl lactate, etc. may be used. The photoresist mayalso be used by developing the pattern in aqueous alkaline developerused in removing exposed photoresists. The neutral layer on thesubstrate still maintains its neutrality after the photoresistprocessing steps. Over the patterned neutral layer, FIG. 4 c, thecomposition comprising the block copolymer is coated and treated (suchas annealing) to form a self directed alignment contact hole pattern ofalternating segments of the block copolymer. A layer which remainsneutral is required to cause the desired orientation of the blockcopolymer to give regions of high etch resistance and regions of lowetch resistance, such that pattern multiplication can be achieved; ifthe neutral layer was not sufficiently neutral then an undesirableorientation perpendicular to one shown would be achieved. A subsequentetch then removes the highly etchable blocks of the block copolymer,leaving a patterned surface with very high resolution, as shown in FIG.4 d. Typical etch would be a wet or plasma etch as described previously.The pattern may then be transferred in the lower stack layers by plasmaetching. Typical etch would be plasma etch dependent on the substrate.This process can be used for both pattern rectification and patternpitch frequency multiplication.

The above processes describe novel processes that can be practiced. Theprocess can use the novel neutral layer composition of the presentinvention.

Each of the documents referred to above are incorporated herein byreference in its entirety, for all purposes. The following specificexamples will provide detailed illustrations of the methods of producingand utilizing compositions of the present invention. These examples arenot intended, however, to limit or restrict the scope of the inventionin any way and should not be construed as providing conditions,parameters or values which must be utilized exclusively in order topractice the present invention.

EXAMPLES

The molecular weight of the polymers was measured with a Gel PermeationChromatograph.

Example 1 Synthesis of Neutral Polymer 1

A solution was prepared containing 0.1642 g of AIBN, 2.6129 g of4-vinylbenzocyclobutene (0.0200 mole), 2.0944 g of styrene (0.0201 mole)and 6.001 g of methyl methacrylate (0.0599 mole) in a 250 ml flask witha magnetic bar and cold water condenser. To this solution was then added25.44 g of 2-butanone giving a clear solution after stirring. Afternitrogen gas was passed to purge for 30 minutes, the flask was immersedin 80° C. oil bath. Polymerization was carried out at this temperaturefor 19 hours. The reaction solution was then allowed to cool to roomtemperature and poured slowly into methanol with stirring to precipitatethe crude polymer. The crude polymer obtained was isolated by filtering.The polymer was purified by dissolving it into 2-butanone andprecipitated again in methanol. The purified polymer was dried in a 50°C. vacuum oven until constant weight (6.8 g). The polymer had a M_(w) of18515 g/mol and M_(n) of 11002 g/mol. This polymer was designated inTable 1 as 20 mole % 4-vinylbenzocyclobutene and 60% MMA, for selfassembly blending experiments.

Example 2 Synthesis of Neutral Polymer 2

A solution was prepared containing 0.165 g of AIBN, 2.6188 g of4-vinylbenzocyclobutene (0.0201 mole), 6.2705 g of styrene (0.0602 mole)and 2.0022 g of methyl methacrylate (0.0200 mole) in a 250 ml flask witha magnetic bar and cold water condenser. To this solution was then added25 g of 2-butanone giving a clear solution after stirring. Afternitrogen gas was passed to purge for 30 minutes, the flask was immersedin a 80° C. oil bath. Polymerization was carried out at this temperaturefor 22 hrs. The reaction solution was then allowed to cool to roomtemperature and poured slowly into methanol under stirring toprecipitate the crude polymer. The crude polymer obtained was isolatedby filtering. The polymer was purified by dissolving it into 2-butanoneand precipitated it again in methanol. The purified polymer was dried ina 50° C. vacuum oven until constant weight (5.8 g). The polymer had anM_(w) of 16,180 g/mol and M_(n) of 9,342 g/mol. This polymer wasdesignated in Table 1 as 20 mole % 4-vinylbenzocyclobutene and 20% MMAfor self assembly blending experiments.

Example 3 Synthesis of Neutral Polymer 3

A solution was prepared containing 0.33 g of AIBN, 7.81 g of4-vinylbenzocyclobutene (0.0600 mole), 10.45 g of styrene (0.100 mole)and 4.0 g of methyl methacrylate (0.0399 mole) in a 300 ml flask with amagnetic bar and cold water condenser. To this was added 52.6 g of2-butanone giving a clear solution after stirring. After nitrogen gaswas passed to purge for 30 minutes, the flask was immersed in an 80° C.oil bath. Polymerization was carried out at this temperature for 20hours. The reaction solution was allowed to cool to room temperature andpoured slowly into methanol under stirring to precipitate the crudepolymer. The crude polymer obtained was isolated by filtering. Thepolymer was then purified by dissolving it into 2-butanone andprecipitated into methanol again. The purified polymer was dried in a50° C. vacuum oven until constant weight (11.6 g). The polymer had aM_(w) of 17086 g/mol and M_(n) of 10005 g/mol. This polymer wasdesignated in Table 2 as 30 mole % 4-vinylbenzocyclobutene and 20% MMAfor self assembly blending experiments.

Example 4 Synthesis of Neutral Polymer 4

A solution was prepared containing 0.323 g of AIBN, 7.81 g of4-vinylbenzocyclobutene (0.0600 mole), 2.09 g of styrene (0.0200 mole)and 12.03 g of methyl methacrylate (0.1201 mole) in a 300 ml flask witha magnetic bar and cold water condenser. To this was added 51.8 g of2-butanone giving a clear solution after stirring. After nitrogen gaswas passed to purge for 30 minutes, the flask was immersed in an 80° C.oil bath. Polymerization was carried out at this temperature for 21hours. The reaction solution was allowed to cool to room temperature andpoured slowly into methanol under stirring. The polymer obtained wasisolated by filtering. The polymer was purified by dissolving in2-butanone and precipitated in methanol again. The purified polymer wasdried in a 50° C. vacuum oven until constant weight (14.5 g). Thepolymer had an M_(w) of 22,469 g/mol and M_(n) of 12370 g/mol. Thispolymer was designated in Table 2 as 30 mole % 4-vinylbenzocyclobuteneand 60% MMA for self assembly blending experiments.

Example 5 Block Copolymer Formulation I

The block copolymer from Polymer Source Inc. (124 Avro Street, Dorval(Montreal), Quebec, Canada) (P8966-SMMA) 22K-b-22K MMA-Styrene (Mw of44K Polydispersity (PD) 1.09) was dissolved in PGMEA to form a 1.5weight % solution and filtered through a 0.2 micron PTFE filter.

Example 6 Block Copolymer Formulation 2

The block copolymer from Polymer Source Inc. (P2449-SMMA) 18K-b-18KMMA-Styrene (Mw of 36K Polydispersity 1.07) was dissolved in PGMEA toform a 1.5 weight % solution and filtered through a 0.2 micron PTFEfilter.

Example 7 Screening Experiment 1

Finger Print Test Method

The neutral layer compositions for testing were prepared as 0.7 wt %solution in PGMEA solvent using the individual polymer or polymer blendsas indicated in Table 1. The solution from which the blended polymerlayer were spun consisted of a wt % blend of a 60% MMA neutral polymer(Synthetic Example 1) with a 20% MMA neutral polymer (Synthetic Example2).

A film of AZ ArF 1C5D (an antireflective coating composition availablefrom AZ Electronic Materials, Somerville, USA) was formed on a siliconwafer with a film thickness of 26.6 nm after a bake of 255° C. for 1minute. Then a layer of the neutral polymer or polymer blend was formedwith a film thickness of 19 nm after a neutralization bake of 255° C.for 2 minutes. Over the neutral layer was coated a layer of a blockcopolymer with a film thickness of 40 nm after an annealing bake of 225°C. for 2 minutes from either the block copolymer solution 1 from Example5 (22k-b-22k MMA/STY) or the block copolymer solution 2 from Example 6(18k-b-18k). The formulations and results are given in Table 1. Aneutral result in Table 1 for line/space pattern shows that the blockpolymer was able to successfully form a self directed assembly of thepolymer over the neutral layer as was seen by a fingerprint image seenin a scanning electron microscope.

Table 1 summarizes experiments in which the neutral polymer of syntheticexample 1 and 2 were blended to ascertain if self assembly with blockcopolymer formulation 1 was occurring through the finger print test. Forline/space (L/S) application the block copolymer block phase-separatesfrom each other and align perpendicularly with the substrate because ofits neutrality to either block segment forming a swirling pattern willform resembling finger print but with regular intervals between theswirls indicating the phase separated regions region of the blockcopolymer oriented perpendicularly to the surface of the neutralsurface. The data in Table 1 indicates that a wide range of blendsranging from 20 mole % MMA to 60 mole % MMA can be made while retainingneutrality of the neutral layer composition.

TABLE 1 Self Assembly on Neutral Layers consisting of blends of Polymerscontaining 20% 4-vinylbenzocyclobutene Finger Print Finger Print NeutralLayer MMA mole % Neutral layer Neutral layer Neutrality ResultNeutrality Result Formulation in the blended polymer 1 polymer 2 L/SPattern L/S Pattern Example # polymer mixture Weight % Weight %22k-b-22k bcp 18k-b-18k bcp 1 20 0 100 Neutral Neutral 2 25 13 87Neutral Neutral 3 30 25 75 Neutral Neutral 4 35 38 62 Neutral Neutral 540 50 50 Neutral Neutral 6 45 63 37 Neutral Neutral 7 50 75 25 NeutralNeutral 8 55 88 12 Neutral Neutral with many defects 9 60 100 0 Neutralwith Neutral with many defects many defects

Example 8 Screening Experiment 2

Finger Print Test Method

The neutral layer compositions for testing were prepared as 0.7 wt %solution in PGMEA solvent using the individual polymer or polymer blendsas indicated in Table 2. The solution from which the blended polymerlayer were spun consisted of a wt % blend of a 20% MMA neutral polymer(Synthetic Example 3), with a 60% MMA neutral polymer (Synthetic Example4).

A film of AZ ArF 1C5D (an antireflective coating composition availablefrom AZ Electronic Materials, Somerville, USA) was formed on a siliconwafer with a film thickness of 26.6 nm after a bake of 255° C. for 1minute. Then a layer of the neutral polymer or polymer blend was formedwith a film thickness of 19 nm after a neutralization bake of 255° C.for 2 minutes. Over the neutral layer was coated a layer of a blockcopolymer with a film thickness of 40 nm after an annealing bake of 225°C. for 2 minutes from either the block copolymer solution 1 (22k-b-22kMMA/STY). The formulations and results are given in Table 2. A neutralresult in Table 2 shows that the block polymer was able to successfullyform a self directed assembly of the polymer over the neutral layer.

Table 2 summarizes results in which the polymer of synthetic example 3was blended with the polymer of synthetic example 4 and neutrality wastested through the “finger print test”. For the test result ‘neutral’ inthe L/S application designates the domains of block copolymer alignedperpendicularly to the substrate due to the neutrality of the film toform a swirling pattern resembling a finger print but with regularintervals between the swirls indicating the phase separated regions ofthe block copolymer oriented perpendicularly to the surface of theneutral. Thus, a neutral result shows that the neutral layer functionedsuccessfully to force the correct orientation of the block copolymer.

TABLE 2 Self Assembly on Neutral Layers consisting of blends of Polymerscontaining 30% 4-vinylbenzocyclobutene Neutral Neutral Neutral Layer MMAmole % layer layer Formulation in the blended polymer 3 polymer 4Neutral Example # polymer mixture Weight % Weight % pattern 10 20 100 0neutral 11 25 87 13 neutral 12 30 75 25 neutral 13 35 62 38 neutral 1440 50 50 neutral 15 45 37 63 neutral 16 50 25 75 neutral 17 55 13 87neutral 18 60 0 100 neutral with many defects

Example 9

The neutral layer composition for testing was prepared as 0.7 wt %solution in PGMEA solvent using the single neutral polymer made fromfeed ratio 40% MMA, 30% Styrene, and 30% 4-vinylbenzocyclobutane. Alayer of the neutral polymer was formed with a film thickness of 19 nmafter a neutralization bake of 255° C. for 2 minutes. Over the neutrallayer was coated a layer of a block copolymer with a film thickness of40 nm after an annealing bake of 225° C. for 2 minutes from the blockcopolymer solution 1 (22k-b-22k MMA/STY). SEM inspection shows that theblock polymer was able to successfully form a self directed assembly ofthe polymer over the neutral layer.

Example 10

Soaking test: The neutral polymer blend (Formulation #18 described inTable 2) was coated and baked at 240° C. for 2 min to form a film of17.6 nm. The film was soaked with an edge bead remover solution(PGME/PGMEA:70/30) for 30 seconds. The film thickness was measured to be17.8 nm after the soaking process, which indicates no detectable filmloss.

Example 11

The neutral polymer blend (Formulation #18 described in Table 2) wasdeposited and baked at 255° C. for 2 min to form a film of 16 nm. Overthe neutral layer was coated a layer of photoresist AZ AX2110P(available from AZ Electronic Materials USA Corp., Somerville, N.J.) andbaked at 110° C. for 60 seconds so as to obtain a 120 nm film. This filmstack was flood exposed with a 193 nm Nikon 306D scanner at dose of 20mJ/cm² in a open-frame mode. A post exposure bake at 110 C for 60seconds was applied. The wafer was developed with AZ MIF300 (availablefrom AZ Electronic Materials USA Corp., Somerville, N.J.) for 30seconds. The block copolymer solution of Block Copolymer formulation 1was coated on the substrate and annealed at 255° C. for 2 minutes (FT 29nm). The wafer was analyzed in a CD SEM (Applied Materials Nano 3D)where it was seen that the block polymer was able to successfully form aself directed assembly over the neutral layer, which indicates perfectneutrality was maintained after the complete photoresist exposureprocess. Thus, no damage to the neutral layer from the exposure processwas observed.

Example 12 Comparative Results

AIBN (0.4944 g, 0.003 mol), 4-vinylbenzocyclobutene (0.6543 g, 0.005mol), styrene (16.54 g 0.14 mol), methyl methacrylate (10.52 g, 0.105mol) and 90 ml of 2-butanone were charged in a 250 ml flask equippedwith a magnetic stirrer, water condenser and gas bubbler. After nitrogengas was passed to purge for 30 minutes, the flask was immersed in a 80°C. oil bath and stirred for 19 hrs. The reaction mixture was cooled toroom temperature and the solution was poured slowly into methanol (2.5L) under stirring. The polymer obtained was isolated by filteringfollowed by reprecipitation from 2-butanone solution in methanol, thendried in a 50° C. vacuum oven until constant weight of 16.37 g wasobtained. The polymer yield was 59%. The polymer had a Mn of 10218 g/moland Mw of 15854 g/mol with PD of 1.55. A 0.7 wt % solution of thepolymer in PGMEA was formulated as a comparative formulation

A comparison test was conducted with a formulation of the abovecomparative polymer and the novel formulation Example 14 from Table 2.

The two solutions, both 0.7 wt % solution of the polymer in PGMEA, werecoated separately on silicon wafers followed by a bake at 255° C. for 2minutes. The films were then subjected to a rinse with AZ EBR7030 (anorganic solvent mixture) for 30 seconds. Film thicknesses were measuredthereafter. The results are shown in Table 3.

TABLE 3 Impacts of solvent rinse Comparative Formulation Formulation 14Film Film Thick- Standard. Thick- Standard. ness nm Deviation*. ness nmDeviation* Before Solvent 18.3 0.3 18.5 0.3 Rinse After Solvent 3.7 2.118.1 0.4 Rinse Film Loss 14.6 — 0.4 — *25 measurements

For Formulation 14, the film thickness was unchanged after the solventrinse. However, significant film loss (14.6 nm) was observed with thecomparative polymer (2 mole % 4-vinylbenzocyclobutene).

The two solutions of comparative formulation and formulation 14, both0.7 wt % solution of the polymer in PGMEA, were coated separately onsilicon wafers followed by a bake at 255° C. for 2 minutes. Both thecoatings were rinsed with AZ EBR7030 for 30 seconds and spin dried; andthen spin coated with poly(styrene-b-methyl methacrylate) blockcopolymer solution (1.5 wt % in PGMEA) to form a layer of 40 nm. Thefilms were annealed at 255° C. for 2 minutes to promote the alignment ofthe block copolymer. The wafers were then inspected in a CD SEM (NanoSEM3D). The comparative formulation gave a film with many defects. TheFormulation 14 gave good alignment and separation of the domains withgood pattern uniformity with no defects.

The two solutions of comparative formulation and formulation 14, both0.7 wt % solution of the polymer in PGMEA, were coated separately onsilicon wafers followed by a bake at 255° C. for 2 minutes. Both thecoatings were not rinsed with solvent and then spin coated withpoly(styrene-b-methyl methacrylate) block copolymer solution (1.5 wt %in PGMEA) to form a layer of 40 nm. The films were annealed at 255° C.for 2 minutes to promote the alignment of the block copolymer. Thewafers were then inspected in a CD SEM (NanoSEM 3D). The comparativeformulation gave a film with many defects and no self alignment of theblock copolymer. The Formulation 14 gave good alignment and separationof the domains with good pattern uniformity with no defects.

Example 13 Graphoepitaxy

An antireflective coating material AZ ArF-1C5D was coated on a 200 mmbare silicon wafer. The coated film was subjected to a bake at 255° C.for 1 minute to obtain a film thickness of 26.5 nm. A layer of NeutralLayer Formulation #14 (16 nm), described in Table 2, was coated on topof the ArF-1 C5D film followed by a bake at 255° C. for 2 minute. On theabove described stack, a photoresist process was carried out whichconsisted of coating with the resist ARX3520 (JSR Micro) and baking at130° C./60 seconds so as to obtain a 70 nm film. This film stack wasexposed with a Nikon 306 D scanner. A PEB at 115° C. for 1 minute wasapplied. The wafer was developed with methyl n-amyl ketone (MAK) for 30seconds. A bake at 200° C. for 2 minutes was applied to harden thephotoresist pattern. The block copolymer solution of Block Copolymerformulation 1 was coated on the photoresist pattern and annealed at 225°C. for 2 minutes (FT 40 nm). The wafer was analyzed in a CD SEM (AppliedMaterials Nano 3D) where it was seen that a pattern was formed by theblock copolymer within the photoresist pattern. Thus the neutral layersuccessfully was used to define narrow lines and spaces within theoriginal photoresist pattern.

Example 14 Chemoepitaxy

An antireflective coating material AZ ArF-1C5D was coated on a 200 mmbare silicon wafer. The coated film was subjected to a bake at 255° C.for 1 minute to obtain a film thickness of 26.5 nm. A layer of NeutralLayer Formulation #14 (16 nm), described in Table 2, was coated on topof the ArF-1C5D film followed by a bake at 255° C. for 2 minutes. On theabove described stack, a photoresist process was carried out, whichconsisted of coating with a positive photoresist from Shin-Etsu Chemicaland baking at 100° C./60 sec so as to obtain a 90 nm thick film. Thisfilm stack was exposed with a 193 nm Nikon 306 D scanner. A postexposure bake of 90° C. was applied. The wafer was then developed withn-butyl acetate for 30 seconds. The patterned wafer was then etched withan oxygen plasma in a ULVAC NE-5000N Etcher for 2 seconds to transfer anarrow trench (30-45 nm) removing the neutral layer. The photoresistpattern was then stripped using AZ EBR7030(PGMEA(30)/PGME(70)). Theblock copolymer solution of Block Copolymer formulation 1 was coated onthe substrate and annealed at 225° C. for 2 minutes (FT 40 nm). Thewafer was analyzed in a CD SEM (Applied Materials Nano 3D) where it wasseen that a 6 times multiplied directed self aligned pattern relative tothe original photoresist pattern was formed by the block copolymer. Thusthe neutral layer successfully was used to define narrow lines andspaces from the original photoresist pattern.

The invention claimed is:
 1. A process for forming an image bygraphoepitaxy comprising: a) forming a coating of a neutral layer on asubstrate; b) heating the neutral layer to form a crosslinked neutrallayer; c) providing a coating of a photoresist layer over thecrosslinked neutral layer; d) forming a pattern in the photoresist; e)applying a block copolymer comprising an etch resistant block and highlyetchable block over the photoresist pattern and annealing until directedself assembly occurs; and, f) etching the block copolymer, therebyremoving the highly etchable block of the copolymer and forming apattern, wherein the neutral layer comprises: (i) at least one randomcopolymer of structure (I) having at least one unit of structure (1), atleast one unit of structure (2) and at least one unit of structure (3)

where R₁ is selected from the group consisting of a C₁-C₈ alkyl, C₁-C₈fluoroalkyl, C₁-C₈ partially fluorinated alkyl moiety, C₄-C₈ cycloalkyl,C₄-C₈ cyclofluoroalkyl, C₄-C₈ partially fluorinated cycloalkyl, and aC₂-C₈ hydroxyalkyl; R₂, R₃ and R₅ are independently selected from agroup consisting of H, C₁-C₄ alkyl, CF₃ and F; R₄ is selected from thegroup consisting of H, C₁-C₈ alkyl, C₁-C₈ partially fluorinated alkylmoiety and C₁-C₈ fluoroalkyl, n ranges from 1 to 5, R₆ is selected fromthe group consisting of H, F, C₁-C₈ alkyl and a C₁-C₈ fluoroalkyl and mranges from 1 to 3, and wherein the neutral layer has unit 1 rangingfrom about 20 mole % to about 80 mole %; unit 2 ranging from about 20mole % to about 80 mole % and unit 3 ranging from about 15 mole % toabout 45 mole %.
 2. The process of claim 1 where the photoresist patternis formed by imaging lithography selected from a group consisting ofe-beam, broadband, 193 nm immersion lithography, and radiation where thewavelength is selected from the group consisting of 13.5 nm, 193 nm, 248nm, 365 nm and 436 nm.
 3. The process of claim 1, where the photoresistis a positive or negative tone developable photoresist.
 4. A process forforming an image by chemoepitaxy comprising: a) forming a coating of aneutral layer on a substrate; b) heating the neutral layer to form acrosslinked neutral layer; c) providing a coating of a photoresist layerover the crosslinked neutral layer; d) forming a pattern in thephotoresist layer to remove the unexposed photoresist, thereby formingan uncovered crosslinked neutral layer region; e) treating the uncoveredcrosslinked neutral layer region, f) removing the photoresist, g)applying a block copolymer comprising an etch resistant block and highlyetchable block over the neutral layer and annealing until directed selfassembly occurs; and, h) etching the block copolymer, thereby removingthe highly etchable block of the copolymer and forming a pattern,wherein the neutral layer comprises: (i) at least one random copolymerof structure (I) having at least one unit of structure (1), at least oneunit of structure (2) and at least one unit of structure (3)

where R₁ is selected from the group consisting of a C₁-C₈ alkyl, C₁-C₈fluoroalkyl, C₁-C₈ partially fluorinated alkyl moiety, C₄-C₈ cycloalkyl,C₄-C₈ cyclofluoroalkyl, C₄-C₈ partially fluorinated cycloalkyl, and aC₂-C₈ hydroxyalkyl; R₂, R₃ and R₅ are independently selected from agroup consisting of H, C₁-C₄ alkyl, CF₃ and F; R₄ is selected from thegroup consisting of H, C₁-C₈ alkyl, C₁-C₈ partially fluorinated alkylmoiety and C₁-C₈ fluoroalkyl, n ranges from 1 to 5, R₆ is selected fromthe group consisting of H, F, C₁-C₈ alkyl and a C₁-C₈ fluoroalkyl and mranges from 1 to 3, and wherein the neutral layer has unit 1 rangingfrom about 20 mole % to about 80 mole %; unit 2 ranging from about 20mole % to about 80 mole % and unit 3 ranging from about 15 mole % toabout 45 mole %.
 5. The process of claim 4 where the photoresist patternis formed by imaging lithography selected from a group consisting ofe-beam, 193 nm immersion lithography, broadband, and radiation whereinthe wavelength is selected from the group consisting of 13.5 nm, 193 nm,248 nm, 365 nm and 436 nm.
 6. The process of claim 4, where thephotoresist is a negative or positive tone developable photoresist.
 7. Aprocess for forming an image by chemoepitaxy comprising: a) forming acoating of a neutral layer on a substrate; b) heating the neutral layerto form a crosslinked neutral layer; c) providing a coating of aphotoresist layer over the crosslinked neutral layer; d) forming apattern in the photoresist layer; e) applying a block copolymercomprising an etch resistant block and highly etchable block over thephotoresist pattern and annealing until directed self assembly occurs;and, f) etching the block copolymer with a plasma, thereby removing thehighly etchable block of the copolymer and forming a pattern, whereinthe neutral layer comprises: (i) at least one random copolymer ofstructure (I) having at least one unit of structure (1), at least oneunit of structure (2) and at least one unit of structure (3)

where R₁ is selected from the group consisting of a C₁-C₈ alkyl, C₁-C₈fluoroalkyl, C₁-C₈ partially fluorinated alkyl moiety, C₄-C₈ cycloalkyl,C₄-C₈ cyclofluoroalkyl, C₄-C₈ partially fluorinated cycloalkyl, and aC₂-C₈ hydroxyalkyl; R₂, R₃ and R₅ are independently selected from agroup consisting of H, C₁-C₄ alkyl, CF₃ and F; R₄ is selected from thegroup consisting of H, C₁-C₈ alkyl, C₁-C₈ partially fluorinated alkylmoiety and C₁-C₈ fluoroalkyl, n ranges from 1 to 5, R₆ is selected fromthe group consisting of H, F, C₁-C₈ alkyl and a C₁-C₈ fluoroalkyl and mranges from 1 to 3, and wherein the neutral layer has unit 1 rangingfrom about 20 mole % to about 80 mole %; unit 2 ranging from about 20mole % to about 80 mole % and unit 3 ranging from about 15 mole % toabout 45 mole %.
 8. The process of claim 7 where the photoresist patternis formed by imaging lithography selected from a group consisting ofe-beam, broadband, 193 nm immersion lithography, and radiation whereinthe wavelength is selected from the group consisting of 13.5 nm, 193 nm,248 nm, 365 nm and 436 nm.
 9. The process of claim 7, where thephotoresist is a negative or positive photoresist.